Yunnan Observatories’ 40-meter radio telescope has been actively involved in the joint observations of very long baseline interferometers (VLBI). It has contributed a lot of valuable data to VLBI networks such as Chinese VLBI Network (CVN), European VLBI Network (EVN), and International VLBI Service (IVS).

In order to improve VLBI observation capability of Yunnan Observatories to meet the joint observations requirements of VLBI, the Radio Astronomy Research Group purchased the second generation digital baseband converter (DBBC2) in 2018.

DBBC2 was developed by the HAT laboratory of Italy, it is the latest generation of stable VLBI observation terminals. Compared with the first generation VLBI observation terminal, it has higher data rate, more observation modes and other advantages.

On June 12, 2019, the 40-meter telescope of Yunnan Observatories participated in the Network Monitor Experiments (NME) of EVN with DBBC2, and the observation code was N19X1.

In the observation, the 40-meter telescope successfully obtained the fringes with Effelsberg telescope of German (see Figure 1), which is the first fringe that we used DBBC2 in a real observation. The single channel fringe is as follow:

Figure 1 shows the cross-correlation plot of Effelsberg and Km stations. The X-axis is the time delay and the Y-axis is the correlation amplitude.

Obtaining the clear fringes between the radio telescopes in a VLBI observation indicates the coherence of the data between the telescopes. It is an important premise for the VLBI observation.

According to the result of the VLBI observation, it can be confirmed that we have upgraded the VLBI terminal successfully.

The improvement of the VLBI observation capability of the 40-meter telescope will enable it to provide more quality and better data, which will help the Yunnan Observatories become more important in the VLBI observation and research.

About the details, see  here:

http://old.evlbi.org/tog/ftp_fringes/N19X1/scan08/index.html

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